How do I?

T

trapper

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I need to "drill" small (4mm + 6.5mm) hex holes in brass aluminium and copper rod.
Unfortunately ,other than various resins, I have no casting ability
Broaching and EDM is not available to me, well at least at affordable rates can anyone help or advise please

Steve
PS I need each part to be osd 12 mm round and 28mm in length
 
Other than using a broach, the only way that I can think of would be to use a toolbit in your lathe the width of one side of the hex. Drill a hole as close to the size of your hex across the flats, then run the toolbit in on the carriage with the chuck locked to cut your flat side. Rotate the chuck 60 degrees and repeat. Granted, there is a lot of math and setup that I left out, but that is the process in a nutshell.
 
A crude, simple, cheap way you might consider is to get a hex key the desired size and hammer-forge the bar around it. Start with material larger than your finished size, drill a hole just large enough to pass the hex, and hammer and rotate, repeat until done. You'll have to press out the hex key, but as long as the material is soft, like the ones you mentioned, this will work. You may have to, and probably should, stop and anneal the material a time or two during the process.
 
How deep do they need to be? I think you're going to end up having to drill and then broach them, but if they are not very deep you might get away with a cheap and brutal approach to broaching.
 
Flutedchamber beat me to it... Oh, what the heck is a mm :dunno:? I thought you Brits invented the English standard measurement system, hence the term...
 
IIRC,a MM is about .394". Correct me if I'm wrong. A foot is ABOUT 30 cm. I just cannot visualize the size of an object when some book says its 134 cm. long. Just not raised on it. I have to make a crude mental conversion. And,buying eggs 10 to a package in England was just annoying!!!!!

A friend,who runs the machine shop at NASA at Langley,20 years younger than I,has to convert his blue prints to inches before making the part!!
 
George, a millimeter is ~0.03937. I use 0.040 for my mental conversions. Meter is 39.37, or 39 3/8" for mental use.

So, a dozen eggs in England is 10? I don't like the Metric dozen then, for sure!
 
Sorry,Tony. I was .0004" off!!!:):):) (but,those tenths add up) Well,that's what I get for becoming an old duff. BUT,I do know where to look such stuff up when I need to know!!

I think that's what someone called being educated: Knowing where to look it up!! For quick reference,I can consult my trusty Leatherman,which has inch and metric scales on it.
 
A decent "down & dirty" method is to take a hex wrench in the size wanted, cut off a piece about 1/2 -3/4" longer than the holes desired, mount the piece in a drill chuck and present it to the side of a bench grinder stone trying for a concave end having crisp edges. Drill your hole to the diameter of the flats and drive the hex wrench into the hole with an arbor press or with a hefty hammer (a touch with a counter sink on the hole will ease the starting) Getting it started can be the trick, if no arbor press, using the drill press or mill might get it started.

This is not as neat as a broached hole, but gives a surprisingly serviceable hex.
 
Hex keys are cheap so why not just make a broach from hex keys. It'll work good for the mentioned metals. Just grind the key into a taper where the botom 1/4" (6mm) or so has no flats and is =< the hole size chuck it up and use a cutoff wheel to grind the teeth about every 5mm. Set the ring on a bushing and drive the key through. You may have to cut several theeth on the top (straight) section to make "spring cuts".

If you screw it up just go buy another key at the hardware store. You can usually buy singles out of the nuts/bolts trays vice a whole set.

Steve
 
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